1. Field of the Invention
The present invention relates to a single-headed piston type swash plate compressor used for a vehicle air-conditioning system etc.
2. Description of the Related Art
The refrigeration circuit used in a vehicle air-conditioning system includes a compressor for compressing a refrigerant gas. This compressor comes in various forms such as variable displacement types and fixed displacement types. More specifically, fixed displacement type compressors include not only single-headed piston type swash plate compressors, but also double-headed piston type swash plate compressors. Variable displacement type compressors also include not only single-headed piston type swash plate compressors, but also double-headed piston type swash plate compressors.
Among these compressors, a general single-headed piston type swash plate compressor defines and forms inside its housing cylinder bores, a crank chamber, a compression chamber, a suction chamber, and a discharge chamber. Each cylinder bore accommodates a single-headed piston so that it may reciprocate. Further, a drive shaft supported rotatably by the housing is driven by an engine or another external drive source. The swash plate is supported by the drive shaft to be able to synchronously rotate with the drive shaft. A pair of shoes is accommodated in a pair of shoe seats provided at an engagement portion in the piston, to drive the piston and is provided at the front and rear of the swash plate.
Here, since each piston is a single-headed piston having a head at only one of the front and rear of the swash plate, the compressor is a single-headed piston type swash plate compressor. Further, if the swash plate is provided at a certain inclination angle with respect to the drive shaft, the compressor is a fixed displacement single-headed piston type swash plate compressor. If the swash plate is provided to be variable in the inclination angle with respect to the drive shaft and the pressure in the crank chamber can be adjusted by a control valve to change the inclination angle and adjust the discharge capacity, it is a variable displacement single-headed piston type swash plate compressor.
In this single-headed piston type swash plate compressor, if the drive shaft is driven by an external drive source, the swash plate synchronously rotates, so the pistons reciprocate in the cylinder bores. Due to this, each cylinder bore forms a compression chamber with the head of the piston, so when the piston is in the suction stroke, low pressure refrigerant gas is sucked into the compression chamber from the suction chamber connected to an evaporator of the refrigeration circuit. When the piston is in the compression stroke, high pressure refrigerant gas is discharged to the discharge chamber from the compression chamber. This discharge chamber is connected to a condenser of the refrigeration circuit. The refrigeration circuit is used as a vehicle air-conditioning system for air-conditioning a vehicle. During this time, in the swash plate compressor, the slidability of the sliding portions between the swash plate and the shoes is ensured by a mist of lubricating oil contained in the refrigerant gas.
In the above single-headed piston type swash plate compressors of the related art, however, the shoes were mainly comprised of a ferrous material, such as SUJ2 according to the Japan Industrial Standards (JIS), and had the disadvantage that they were heavy. This disadvantage was present in both fixed displacement swash plate compressors and variable displacement swash plate compressors.
An object of the present invention is to provide a lighter single-headed piston type swash plate compressor.
According to the present invention, there is provided a single-headed piston type swash plate compressor comprised a housing internally defining and forming cylinder bores, a crank chamber, a suction chamber, and a discharge chamber; a drive shaft driven by an external drive source and supported rotatably by the housing; a swash plate supported by the drive shaft to be rotated synchronously with the drive shaft; a single-headed piston accommodated in each of the cylinder bores to be able to reciprocate therein and to define a compression chamber therein; and a pair of shoes provided at the front and rear of the swash plate so as to be accommodated in the piston and to drive the piston; wherein the shoes are mainly comprised of a resin.
Preferably, each shoe is impregnated with a lubricating oil.
Preferably, the inclination angle of the swash plate is variable with respect to the drive shaft and the pressure in the crank chamber can be adjusted by a control valve to change the inclination angle and to adjust the amount of discharge capacity.
Preferably, the swash plate is comprised of a swash plate substrate made of a first metal and a coating formed on the front and rear surfaces of the swash plate substrate for improving the slidability with the first metal.
Preferably, the piston is comprised of a piston substrate made of an aluminum-based material and a coating made of tin plating formed on the shoe seat of the piston substrate, and a semi-spherical convex surface of the shoe and a semi-spherical concave surface of the shoe seat slide against each other.
Preferably, the swash plate is comprised of a swash substrate made of a ferrous material and aluminum sprayed layers formed on the front and rear surface of the swash plate substrate, and resin coats are formed on the aluminum sprayed layers.